Heat Sinks can be classified in terms of manufacturing methods and their final form shapes. The most common types of air-cooled heat sinks include stampings, extrusions, forging, bonded/fabricated fins, die castings and folded fins. Following is an explanation of each technique.
- Stampings: Copper or aluminium sheet metals are stamped into desired shapes. They offer a low cost solution to low density thermal problems. They are suitable for high volume production, because advanced tooling with high speed stamping lowers costs. Additional labor-saving options, such as clips and interface materials, can be factory-applied to help further reduce assembly costs.
- Extrusions: This is the most popular method of manufacturing heat sinks. Extrusion is the process by which long straight metal parts can be produced. It is done by squeezing metal in a closed cavity through a tool, known as a die, using either a mechanical or hydraulic press. After the metal has cooled, it is cut to size based on drawing specifications.
- Forging: This is the process whereby metal is heated and shaped by plastic deformation by suitably applying compressive force. Usually the compressive force is in the form of hammer blows using a power hammer or a press. This method is rarely for heat sink manufacturing but it does fit the need occasionally.
- Bonded/Fabricated Fins: Most air-cooled heat sinks are convection limited and the overall thermal performance of an air-cooled heat sink can often be improved significantly if more surface area can be exposed to the air stream. These high performance heat sinks utilize thermally conductive, aluminium-filled epoxy to bond planar fins onto a grooved extrusion base plate.
- Die Castings: Die casting is where the metal is injected into the mold under high pressure of 1,450-30,500psi. This results in a more uniform part, generally good surface finish and good dimensional accuracy, usually within 0.2% of casting dimension. This means you can make more complex shapes using die casting than you can using other methods such as extrusion.
- Folded Fins: Corrugated sheet metal in either aluminium or copper increases surface area, and subsequently, the volumetric performance. The heat sink is then attached to either a base plate or directly to the heating surface via epoxy or brazing. It is not suitable for high profile heat sinks due to availability limitations and fin efficiency.